Plasma weapons are indeed weak in the early game.
However, later on, they can be quite nice.
My plasma battleships came in extremely handy in this battle:
http://imagemodserver.mine.nu/other/...Tudran2_02.jpg
As a rough count, my (nausea heap) forces numbered approximately 300, while the Pandorans (bluish shiny metal ships) numbered 400 plus significant numbers of fighters.
On the third day of combat that month, the fighter squadrons had long since been wiped out, the missile tubes were completely dry, and only the torpedo boats with damaged engines still had ammo left (since they couldn't get into range and fire)
As the ragged, starving ships flew past the warppoint on yet another attack run, only my Plasmatica class ships were still doing significant damage.
In the end, my Plasma battleships turned a stalemate into a resounding victory.
The optimum range for Heavy Lasers early in the combat is medium to long range, so they stay out of the way of DUC/Plasma ships from both sides. Late in a multi-turn campaign it may better to close in to maximize your damage output since the ammo-using enemy guns will have fallen silent, but if there are any still-live short range DF guns, they will tear you apart.
Overall, heavy lasers are not that great a weapon in most cases. The Plasma shreds ships faster at close range, and Torpedoes deal more damage at long range. If you can afford to specialize your ships, do so.
Heavy lasers are better earlier on with smaller fleets... when optimal range means you can both get in close and demolish a torpedo boat, and stay far away from plasma ships to pick them apart. But if both torpedoes and plasma are present, then heavy lasers don't work so well.
Light laser cannons are always good as point defense however.
The value of lasers is certainly not the sum of damage at each range... after all, you don't get to fire that gun at all ranges each shot. You should consider just one damage value, at the typical range you hope to use it at, to be optimistic.
Using the Laser 1 - Unmounted as in the previous example, that is something lower than 300, every two turns.
A comparable tech level plasma cannon deals 50% more damage while taking the same space. (230 per turn)
So, if you can keep your distance, the laser might win taking no damage. But if you ever get into plasma range, you get roasted alive.
In small, early game combats, the laser ships have plenty of room to move around and avoid getting trapped. As the battles get bigger, weapon range means less and less, until plasma and DUCs become king.
At that point, the only benefit to the long ranged weapons is the fact that you can only fit 50 ships into combat squares right next to enemies... so the number of effective SR ships is limited.
This naturally leads to the re-introduction of good old military manouvers. Pincer attacks, crossing the T, such become quite useful.
After all, if you have surrounded the enemy, then you not only can fit more SR warships on your side of the (circular) front line than the enemy's side... but you also, by default, get to score some easy kills with SR ships vs the lightly armored missile boats typically found in the enemy's rear.
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So, as for missiles. All missiles have infinite range in CBmod. They can only be locked and launched from range 20 due to vagaries of the SE4 hardcode.
If you wish for your antiplanet ships to hit twice, then you could order them to rush in. Most of the time, you should have warships cleaning up the resistance before your glassers do their work, so there will be little return fire.
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PS:
The main failing of your formula is that it overvalues range, particularily when the ranges are short, as in CB. A range 2 vs a range 1 weapon is certainly not twice as powerful.
In one-on-one combat, a range 2 vs range 1 battle is mostly equivalent to a range 8 vs range 7.
The size of a battle is also a huge factor in deciding what weapons are best.
For example;
- If you are fighting with just two or three ships per battle, then long range weapons are the best. Cripple them before they get close, then kill at your leisure.
- If you are fighting with just two or three hundred ships per battle, then short range weapons are king. The enemy can't stay out of range, and short range guns deal far more damage. The short range guns shred the enemy before the long range guns can do very much damage.